Papers by Roy Lichtenheldt
Space Science Reviews, 2016
Computational Methods in Applied Sciences, 2016
Space Science Reviews, 2016
To meet the increasing mobility demands in planetary exploration, there is a need for further det... more To meet the increasing mobility demands in planetary exploration, there is a need for further detailed soil interaction models. Therefore a simulation framework based on the three-dimensional Discrete Element Method (DEM) is developed. This approach implicitly covers the soils grain relocation and the resulting plastic deformations. The model and framework are designated to predict the dynamic interaction with soft soils for development of locomotion equipment and strategies. As the shear strength of granular matter strongly depends on interparticle friction and rotation, a new interparticle contact model is developed. For determining the particle’s contact parameters, a first procedure without the need of preliminary calibration simulations has been designed. First results, which could be used for wheel development are presented. Bevameter measurements are used to set the particles parameters as well as for verification issues.
In order to gain further knowledge about the evolution of terrestrial planets in our inner solar ... more In order to gain further knowledge about the evolution of terrestrial planets in our inner solar system, NASA’s InSight Mission (Interior Exploration using Seismic Investigations, Geodesy and Heat Transfer) aims to investigate Mars’ subsurface. Therefore InSight’s HP3-Instrument (Heatflow and Physical Properties Package), developed by DLR, will measure the heat flux in Mars’ interior. In order to get the instruments down to a final depth of 5m the HP3-Mole is hammering itself below the martian surface deeper than any instrument before. To achieve this challenging goal the HP3-Mole works as a self impelling nail, driven by its inner hammering mechanism. As the achieved depths as well as the needed energy for "digging" strongly depend on the locomotion performance of the Mole, the hammering mechanism has been object to analysis and optimization using numerical multi-body models. While approaching the design limits of mass minimization and performance optimization, mechanical...
As the formation of the rocky planets in our inner solar system has always been a major subject o... more As the formation of the rocky planets in our inner solar system has always been a major subject of scientific interest, NASA’s discovery mission InSight (Interior Seismic Investigations, Geodesy and Heat Transport) intends to gain further knowledge about the interior structure of Mars. In order to understand the processes that lead to planetary evolution, Mars’ seismic as well as thermal properties will be measured. DLR’s HP3-Mole (Heat Flow and Physical Properties Package), an innovative self impelling nail, will hammer itself into the red planet deeper than any other instrument before, in order to measure the heat flux and thermal gradient down to a final depth of 5 m. To achieve this challenging goal, high fidelity simulation models have been used throughout the whole development process. To meet the demands on accuracy, two detailed models were created based on enhanced multi-body dynamics and discrete element techniques. For the most detailed analysis both methods are coupled t...
In consequence of growing interests of science exploration on our solar system’s planets and moon... more In consequence of growing interests of science exploration on our solar system’s planets and moons, increased mobility demands are arising for planetary exploration vehicles. The locomotion capabilities of these systems strongly depend on the interaction with soft granular soils. Thus a major design challenge is to develop suitable solutions for locomotion equipment and strategies. The mastering of these challenges depends on detailed soil interaction models to predict the system behaviour and get a better understanding of the underlying effects. To meet these demands a new soil interaction model based on the three-dimensional Discrete Element Method (DEM) is developed. The strength of granular materials is highly dependent on the grain’s shape and friction. Since non-spherical particles are less computational efficient than spheres, a new interparticle contact model has been developed to mathematically cover the rotational behaviour of anisotropically elongated and angular grains, whi...
Today's growing scientific interest in extraterrestrial bodies increases the necessity of ext... more Today's growing scientific interest in extraterrestrial bodies increases the necessity of extended mobility on these bodies. Thus, planetary exploration systems are facing new challenges in terms of mission planning, obstacle and soil traversability. In order to fit the tight schedules of space missions and to cover a large variety of environmental conditions, experimental test setups are complemented by numerical simulation models used as virtual prototypes. In this context we present an integrated simulation environment which allows for using different available contact models, ranging from simple but real-time capable approximations based on rigid-body modeling techniques up to very accurate solutions based on Discrete Element Method (DEM). For this work, a one-point Bekker based approach and the so-called Soil Contact Model (SCM), which is a multi-point extension of the \textsc{Bekker}-\textsc{Wong} method taking soil deformation into account, are used. These two contact mod...
After a cruise phase of four years, Mascot will land on the asteroid 1999JU3. Due to the complex ... more After a cruise phase of four years, Mascot will land on the asteroid 1999JU3. Due to the complex interaction of the lander with the terrain in low-gravity environments, a certain orientation of Mascot after descent cannot be achieved directly. Thus the mobility unit developed in the DLR Robotics and Mechatronics Center enables Mascot to upright into the nominal position and to relocate by hopping motion. As the dependence of the desired jumping trajectory on the trajectory of the mobility eccentric arm is complex, a suitable trajectory cannot be determined beforehand. As even parabolic flight campaigns do not allow for sufficiently long low-gravity phases, it is also not possible to define the trajectories based on measurements. Additionally the zero or low gravity phase during parabolic flights needs to be quite precise. Thus Mascot’s multibody dynamics model is used to check a priori created trajectories. Therefore the model has been verified using both parabolic flight campaigns ...
In early mission phases, simulation can greatly reduce cost and construction efforts, by reducing... more In early mission phases, simulation can greatly reduce cost and construction efforts, by reducing uncertainties on new, yet to be built space systems such as satellites or planetary rovers. At the DLR institute of system dynamics and control, simulation methods are researched to accurately simulate complex multi-physics systems, utilizing the Modelica modelling language and self-developed tools. The focus of the development is to bridge the gap between the early phase systems engineering, where only rough insight in the systems behavior is available, and the later phases detail studies, where already existing or to be developed hardware is simulated in detail and mostly isolated. The multi-physics approach of Modelica allows interconnecting different domains like electronics, (flexible) multi-body dynamics, propulsion systems, terra-mechanics or algorithms (e.g. path-planning). This allows the user to get a better grasp on the coupled system behavior and to optimize single component...
The penetration performance of the HP^3 heat flow probe is assessed, and applications to the Moon... more The penetration performance of the HP^3 heat flow probe is assessed, and applications to the Moon and Mars are discussed.
The Mobile Asteroid Surface Scout (MASCOT) is already on its way to the C-type asteroid 1999 JU3.... more The Mobile Asteroid Surface Scout (MASCOT) is already on its way to the C-type asteroid 1999 JU3. On 3rd December 2014 at 05:22 CEST, a JAXA H IIA launch vehicle lifted off from the Tanegashima Space Center and the Hayabusa-II spacecraft together with its MASCOT lander began their journey through space. After a cruise of almost four years, Hayabusa-II with MASCOT will reach their target, where MASCOT will descend to the surface of the asteroid. An innovative hopping mechanism, developed at DLR’s Robotics and Mechatronics Center (RMC), allows the lander to upright to nominal position and to relocate on asteroid surface by hopping. A big advantage of this movement principle is the independence of the surrounding environments like rocks or craters due to the fact that all moveable parts are inside the lander. The mobility concept was developed based on Multi-Body-System simulation and verified by a zero-g flight test campaign. This paper gives an overview of the mission, the challenges...
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Papers by Roy Lichtenheldt